The December 2004 Indian Ocean Earthquake triggered a tsunami, that ravaged that nearby countries in a most tragic way:(:(. At least 240,000 people were killed, and countless went missing forever. In fact, the whole Earth rang like a bell, and even the rotation of the Earth was affected, albeit in a minute way. Recently, researchers at Columbia University's Lamont-Doherty Earth Observatory (LDEO) analyzed recordings of the underwater sound produced by the magnitude 9.3 earthquake. Their unique approach enabled them to track the rupture as it moved along the Sumatra-Andaman Fault, raising the possibility that scientists could one day use the method to track underwater earthquakes in near real time and opening new avenues in seismologic research.

Frequency spectrogram of the earthquake sound (Courtesy: LDEO)The researchers found that the first phase encompassed the first three minutes of the eight-minute earthquake, during which the rupture proceeded north at about 1.7 miles per second (2.8 km/sec) from the epicenter. During the second phase, the rupture slowed to 1.3 miles per second (2.1 km/sec) and continued north for another five minutes until it reached a plate boundary where the fault changed from subduction (where one plate is sucked under another) to strike-slip (where the two plates rub against each other). This suggests that had the subduction zone continued, this longest-ever-recorded earthquake might have been even longer!!
The analysis that Maya Tolstoy and her co-author DelWayne Bohnenstiehl used also shows promise for helping officials quickly determine where relief activities are needed. In the case of the Indonesian earthquake, early seismic data indicated that only the southernmost third of the fault was involved. Later analysis revealed that about 750 miles actually ruptured, a finding that was supported by their study:).
A recording of the earthquake can be heard here.